Question

In an examination, 1 mark is awarded for each correct answer while 0.25 marks are deducted for each wrong answer. If an examinee had attempted 80 questions and got 60 marks, then how many problems did he solve correctly ?

a)62
b)64
c)66
d)68
e)70

Answer 1

According to given sum,

let the total correct ans be x.

And total wrong answers be y. then

x+y=80...........i

1 mark is given for 1 correct ans and 0.25 marks are deducted for 1 wrong ans.

=1 (x)-(0.25)y=60

=x-0.25y=60...........ii

subtracting equation ii from i , we get

1.25y =20
y=16.

substitute the value of y in equation i

x+16 =80

x=80-16=64

hence , the ans is option b.

:-)hope it helps u.

Answer 2

let the no.of correct answers be x and wrong answers be y.
mark awarded for each right answer =1
mark deducted for each wrong answer =0.25
total questions attempted =80
=>x+y=80
=>y=80-x

Marks scored =60
=>1x-0.25y=60
=>x-25/100×(80-x)=60
=>x-1/4×(80-x)=60
=>x-20+1/4x=60
=>5/4x=80
=>x=80×4/5
=>x=16×4
=>x=64

So the no.of correct answers is b)64.